The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
The present invention is related to U.S. Pat. No. 8,135,556 and U.S. Published Patent Application US 2013/030444A1, which are hereby incorporated by reference in its entirety. Generally, the afore-mentioned application provides an arrangement for controlling simulation of a coupled hybrid dynamic system. The arrangement comprises a physical test rig configured to drive a physical structural component of the system and to generate a test rig response as a result of applying a drive signal input to the test rig. A processor is configured with a virtual model of the complementary system (herein also “virtual model”) to the physical component (i.e. the virtual model of the complementary system and the physical component comprises the complete hybrid dynamic system). The processor receives a first part of a test rig response as an input and generates a model response of the complementary system using the first part of the received test rig response and a virtual drive as inputs. The processor is further configured to compare a different, second part of the test rig response with the corresponding response from virtual model of the complementary system to form a difference, the difference being used to form a system dynamic response model which will be used to generate the test rig drive signal.
In an embodiment, the processor is further configured to generate the test drive signal, receive the test rig response, generate a response from the virtual model of the complementary system, and compare the test rig response with the response from the virtual model of the complementary system to generate a hybrid simulation process error. The error is then reduced using an inverse of the system dynamic response model, in an iterative fashion until the difference between the response from the virtual model of the complementary system and the test rig response is below a defined threshold.
In one embodiment illustrated in FIGS. 11 and 12 of U.S. Published Patent Application US 2013/0304441A1, which is illustrated herein as FIGS. 1 and 2 with the same reference numbers although the schematic figures are of a different form, a random test rig drive 78′ is played into a test rig 72′ that has a vehicle 80′ installed thereon. The test rig 72′ applies loads and/or displacements to each spindle of the vehicle 80′. The random test rig drive 78′ may be a generic drive, such as a random amplitude, broadband frequency drive, provided to a rig controller 74′ that in turn controls actuators of the test rig 72′. Multiple responses 82′, for instance six degrees of freedom (6 DOF) are obtained from suitable sensors for each spindle and are applied to a virtual model 70′ of the complementary system, in this embodiment, comprising a virtual tire and wheel assembly for each spindle (disembodied tire and wheel, herein also “DWT”). For instance, and without limitation, the multiple responses 82′ can comprise at each spindle, a vertical force, a longitudinal displacement, a lateral displacement, a camber angle and a steer angle. Other responses 84′ from the test rig 72′ are compared with responses 88′ from the virtual model 70′ of the complementary system. Again, for instance, and without limitation, the responses 88′ can comprise a vertical displacement, a longitudinal force, a lateral force, a camber moment and a steer moment. It is to be noted that the force and displacement signals are exemplary only, as other response signals may be provided from the test rig 72′.
The responses 82′ from the test rig 72′ are supplied as inputs to form a random drive 86′ to the virtual model 70′ of the tire and wheel assemblies. The virtual vehicle model 70′ excludes the components under test, in this case the vehicle 80′ less the wheels and tires. The virtual model 70′ responds to the random drive input signals 86′ with random response signals 88′.
In the third step of the process, the random responses 88′ of the virtual model 70′ of the tires and wheels are compared to the associated test rig random responses 84′. A comparison 90′ is performed to form random response differences 92′ (herein comprising forces, moments and displacements). The relationship between the random response differences 92′ and the random rig drives 78′ establishes the system dynamic response model 76′. The determination of the combined system dynamic response model 76′ may be done in an off-line process, such that high powered and high speed computing capabilities are not required. The off-line measurement of the system dynamic response model 76′ measures the sensitivity of the difference in the responses 88′ of the virtual model 70′ of the tires and wheels and rig responses 84′ to the rig inputs when the vehicle 80′ is in the physical system. Further, since there is no need to acquire data, any component can be tested without previous knowledge of how that component is going to respond within a virtual model, or in a physical environment. The off-line measurement of the system dynamic response model 76′ measures the sensitivity of the difference in response 88′ of the virtual model of the complementary system and rig response 84′ to the rig inputs when the component 80′ is in the physical system. Once the relationship between rig drive 78′ and system response difference 92′ has been modeled, an off-line iteration process is performed, as seen in FIG. 2. This may be considered as the test drive development step.
In the iterative process of FIG. 2, which is an off-line iteration, the virtual model 70′ of the DWT is used. The virtual DWT are driven over a virtual test road 79′, to generate response 88′. An additional input to the virtual model 70 of the complementary system, in addition to the virtual test road input 79′ and/or power train and steering 83′ (driver inputs), is shown as reference numeral 86′. The additional model input 86′ to the model 70′ is based on the test rig response 82′ from the test rig 72′ as well the inputs of DWT guidance 85′. The additional model input 86′ is applied simultaneously to the vehicle model 70 during testing. For an initial iteration (N=0), the input 86′ to the virtual model 70 of the complementary system will typically be at zero.
The response 88′ of the virtual model 70′ is compared to the test rig response 84′ from the test rig 72′. This test rig response 84′ is of the same forces and/or displacements as the response 88′ so a comparison can be made by comparator 90′ with the response difference indicated at 92′.
The response difference 92′ is compared to a desired difference 104′ by comparator 106′. Typically, the desired difference 104′ will be set at zero for an iterative control process, although other desired differences may be employed.
The comparison between the response difference 92′ and the desired difference 104′ produces a simulation error 107′ used by the inverse (FRF−1) 77′ of the system dynamic response model 76′ that was previously determined in the steps shown in FIG. 1. A drive correction 109′ is added to the previous test rig drive signal 110′ at 112′ to generate the next test rig drive signal 78′.
The next test rig drive signal 78′ is applied to the test rig 72′ and first and second responses 82′, 84′ are measured. The response 82′ to be applied to the DWT model 70′ and generates via the processor and the virtual DWT model 70′ response 88′ that is compared to test rig response 84′ so as to generate another simulation error 107′. The process applying corrected drives 78′ and generating simulation errors 107′ is repeated iteratively until the resulting simulation error 107′ is reduced to a desired tolerance value.
Following the determination of the final test rig drive signal 78′, the final test rig drive signal 78′ is used in testing of the test component 80′. The test rig drive signal 78′ is an input to the test rig controller 74′ that drives the rig 72′. As indicated above besides the response 82′, the DWT model 70′ also receives as inputs the digital road data 79′, power train & steer inputs to the DWT indicated at 83′ and/or DWT guidance 85′. Hence, performance testing, durability testing and other types of testing may be performed on the physical component 80′, herein a vehicle, without the need for a physical tires and wheels to have been previously measured and tested, or in fact, to even exist.